Method for producing magnetic plates from electrolytic iron



Patented June 27, 1933 UNITED STATES FRANZ PAWLEK OF BERLIN-KARLSHOBST, GERMANY, ASSIGNOB. TO ELEC- CORPORATION OF NEW YORK TRIO COMPANY, A

METHOD r03 rnonocme MAGNETIC PLATES anon nLEc'raoLYrIc moi:

No Drawing. Application filed May 28, 1932, S

For electrotechnical purposes, particularly for the construction of transformers 1t desirable to employ iron plates having as low a hysteresis loss as possible. Apart from. me-

chanical conditions, such as grain size, hardness etc., the shape of the hysteresis curve will be afiected by the other elements in the iron. Each of the elements, oxygen, carbon, sulphur, phosphorus and manganese has a detrimental effect. Although the quantities of sulphur, phosphorus or manganese may be easily reduced in the manufacturing process,

so that they no longer have'a detrimental effeet, the matter is not so simple in the caseof 15 the most detrimental elements oxygen and carbon. However, in actual practice the ad verse eifects of oxygen and carbon have been reduced by the addition'of a small percentage of silicon.

In the case of lectrolytic iron however the conditions are different. When producing such iron from chloride or sulphate baths the quantity of each of the elements, sulphur,

silicon or phosphorus will be about0.001-0.003. per cent and manganese 0.02 per cent; The

carbon will vary within limits from about 0.01-0.04 per cent if the work is carried out without a diaphragm and with an anode material having a low carbon content. The oxygencontent of the electrolytic iron. isvery high with regard to its adverse influence, namely 0.02-0.05 per cent, which is about ten times as much as that contained in a good quality Siemens Martin steel. The oxygen 5' in the electrolytic iron two ways. Inone case, through the enclosed bath residue; this part will be all the greater the more acid the bath is. ;In the other case b it may beintroduced by a basic iron salt which may be in suspension in the bath and which separates out from the electrolyte when the latter is insufiiciently acid, that is when the hydrolytic balance of the corresponding 5 iron salt has been exceeded." These basic salts are positive colloids; they travel to the cathode and settle down in the deposit. Ifthe electrolytic, iron is then annealed in order to drive out the hydrogen and get rid of the stresses which may be presentin the plate, the

may be introduced in erial No. 614,283, and in Germany June 22, 1931.

in the deposit, particuwill react asfollows:

As this balance is entirely displaced to the right at the annealing temperature, (approx. 850) oxidation will occur whilst the hydrogen is escaping. The basic salts thrown down as collo1ds in the deposit will also react on a similar principle. The oxide formed batli residue present larly water and iron,

will dissolve the iron and will'have an extremely prejudicial influence upon the magnetic properties of the iron.

In electrolytic iron, oxides and carbon are present therefore after a short annealing period. These may react with one another as follows: i

This balance is approximately in the middle at the temperatures in question (approx. 850). If on the other hand the COlis continuously removed, the annealing being done in vacuum, the balance will be constantly disturbed and the reaction will take. place from left to right until either no more F eO or no carbon is present. The factor which determines the speed of the reaction is in this case the speed of diffusion of the FeO and C in the iron. As this is very slow,a correspond ingly long annealing period must be adopted. By this means it is possible to remove entirely one of the constituents, oxygen or carbon, according to which of themis present in the smaller amount;

It has been stated above that the carbon 1 content of the electrolytic iron will depend upon the carbon content ,of the anode, whilst carbon inthe iron equivalent to the oxygen.

It is possible when employing, anodes of pure material to obtain a carbon content in the deadding to the bath organic substances posit by oxalic acid, citric acid, succ nic acid such as etc., or water soluble salts of the latter or organic matter present in the extent.

then take place. The car ganic colloids such as gum arabic', gelatine etc, which become positively charged in the bath. The quantity of carbon is approximately proportional to the uantity-of orath. By this means therefore a quantity may be introduced into the iron which is equivalent to the quantity of oxygen.

It is also possible by varying the acid content'of the bath to add a corresponding quantity of oxygen to a predetermined carbon content. The oxygen content of the electrolytic iron will fall somewhat on reducing the acid concentration from pH=2 to pH=2.7 and will then rise enormously when the hydrolytic balance is exceeded. These data are correct for a bath of iron chloride with approximately g Fe/l, a bath temperature of C. and a current of 5 A/dcm The oxygen content will alter accordingly by varymg the conditions of deposition.

It is possible, therefore, during deposition to introduce equivalent quantities of oxy en and carbon into'the electrolytic iron. l3y subsequently annealing in a vacuum the two constituents may then be removed to a great It is also possible, however, to have nonequivalent quantities of carbon and oxygen in the iron. If the carbon is present in excess, the plates are first annealed in an oxidizing atmosphere in order to obtain a corresponding oxygen content, and are subsequently annealed in a-vacuum. A process similar to the temperin of cast iron will 11 reacts with the iron oxide but the reaction will be correspondingly slower since the diffusion conditions are considerably less favorable.

- If the oxygen is in excess, a corresponding quantity of carbon may be added to the iron by carbonizing, for example by annealing in an atmosphere of carbo -dioxide, and on 2. The process of producing magnetic sheet material from electrolytic iron which comprises employing during electrolysis anodes having acarbon content substantially equivalent to the oxygen content of the iron and then annealing the a vacuum. 7

3. The process of producing magnetic sheet material from electrolytic iron which comprises varying the carbon content of the iron by adding organic material to the electrolyte in sufficient quantity to equalize the carbon and oxygencontent of the iron and then annealing theelectrolytic iron in a vacuum.

4. The process of sheet material from electrolytic iron which comprises varying the acidity of the electroelectrolytic iron in ly'te thereby to balance the, carbon and oxy-' gen content of the iron and then annealing the electrolytic material in a vacuum.

5. The process of producing magnetic sheet material from electrolytic iron which comprises annealing the electrolytic material in a carbonizing atmosphere thereby to equalim the carbon and oxygen content of the iron, and thereafter annealing the iron in a vacuum.

In witness whereof, I have hereunto set my hand. i

FRANZ PAWLEK producing magnetic 

